Its usually a penny or two cheaper on the Illinois side at this particular location. Illinois charges sales tax on gas, but Wisconsin's gas tax is higher (3rd highest in the country, I believe) and up until recently Wisconsin prices were artificially higher do to a minimum mark-up law. Thankfully, that 80 year old law was just struck down by the courts so now prices are usually about the same on both sides of the border.


For whatever reason, stations on both sides of the border are usually the cheapest for miles around. This afternoon, I filled up in Beloit for $2.35, but prices in Madison are at $2.49, and both Milwaukee and Rockford are at $2.59.